Maintenance types


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Maintenance types

  1. 1. Motasem Abushanap Maintenance Types RCM and its strategies Definitions & Applications RCM Reactive Preventive PT&I Proactive- small items - subject to wear out - random failure - root cause failure- non critical - consumable - not subjective to analysis- inconsequential - known to failure wear out - age exploration- unlikely to fail pattern - PM induced - failure moods and- redundant failures effect analysis - commissioningReliability Centered Maintenance (RCM):Reliability centered maintenance (RCM): integrates preventive maintenance (PM) with predictivetesting and inspection (PT&I) and repair(known as reactive maintenance), with also proactivemaintenance to increase the probability for a machine to function in the designed way , so it canreaches its designed life cycle with the minimum maintenance costs, and minimum downtime,RCM integrates these strategies and principles to gather so they are optimally integrated, so allstrategies advantages can be achieved, so resulting by maximizing reliability of systems andcomponents while minimizing maintenance cost and downtime.RCM Analysis:The main questions to be asked while analyzing are: 1- What does system/component/device do? 2- What are component/system functions? 3- What functional failures can be occur? 4- What are the likely consequences (seriousness) of these failures? 5- What can be done to reduce the probability of these failures (solutions or improvements, or replacements)?
  2. 2. Motasem Abushanap eng-motasem@hotmail.comRCM objectives (Nowlan & Heap): 1- Insure realization of the inherent safety and reliability levels of the system/components. 2- Restore the system/components to these inherent levels when deterioration occurs. 3- To obtain the information and data necessary for design the improvement and adjustments of these items where their inherent reliability start to be inadequate. 4- To achieve these goals at minimum total cost, including maintenance cost, support costs, and economic consequences of operational failure.Types of Reliability Centered Maintenance (RCM):  Rigorous RCM Approach (classical RCM).  Intuitive RCM Approach (Streamlined/ Abbreviated).RCM Strategies 1- Reactive (repair) maintenance, run to fail maintenance (RTF). 2- Preventive maintenance (PM), time based maintenance. 3- Predictive testing and inspection (PT&I), condition based maintenance. 4- Proactive maintenance.Reactive Maintenance (Run to Fail):reactive maintenance (repair) : referred to break down, repair, fix-when-fail, or run-to-fail (RTF)maintenance , trouble calls (TCs) are typical type of reactive maintenance , when applying thistechnique, maintenance, components repair, or replacement happens only when failure takesplace in the components functional tree, this technique assumes failure is equally likely to happenin any system, component or device, and failure is age related, this leads to identify a specificgroup of repair parts, as being more necessary or desirable that others.Prioritizing Reactive maintenance in a systemPriority Criteria based on consequences of components/systemsnumber description1 Emergency Safety of life or property threatened. Immediate serious impact on mission2 Urgent Continuous facility operation Threatened. Impending serious impact on mission.3 Priority Degrades quality of mission support. Significant and adverse effect on project.4 Routine Redundancy available. Impact on mission insignificant5 Discretionary Impact on mission negligible. Resources available.6 Deferred Impact on mission negligible. Resources unavailable.Preventive Maintenance (PM):Preventive Maintenance (PM): is time based maintenance where maintenance occurs according toa predetermined scheduled plan, it consists of regular scheduled activities such as adjustments,
  3. 3. Motasem Abushanap eng-motasem@hotmail.comreplacements, inspections, calibration, lubrications, repair of systems and components, theschedules done on a predetermined time intervals, ( operating hours , cycles and time), in anattempt to reduce system failure.Depending on the time intervals, preventive maintenance (PM) can result in a significant increasein inspections and routine maintenance, preventive maintenance (PM) also reduces the frequencyand effectiveness of unplanned machine breaks and downtime, for the components and systemwith defined age related wear patterns.Preventive maintenance assumes that overhauls of machinery by disassembly and replacement ofworn parts, restores the machine to a likely new condition with zero harmful effect, this renewaltask based on the perception that new components and systems are less likely to fail than old onesof the same design.Time intervals or interval sets are usually determined by Mean Time Between Failure (MTBF).Predictive Maintenance (Predictive Testing and Inspection (PT &I)):Predictive Maintenance (Predictive Testing and Inspection (PT &I)): it is a condition basedmaintenance, by monitoring the condition of systems and components, uses nondestructive teststechniques, visual inspection, performance records and data to assess the machinery condition,Predictive Maintenance (Predictive Testing and Inspection (PT &I)) replaces periodic timemaintenance that are scheduled only when warranty by components condition, continuinganalysis of components condition monitoring data allows planning and scheduling ofmaintenance activities in advance of serious and functional failures.Methods and ways to determine the condition of components/systems & identify the precursors offailure: 1- Trend analysis. 2- Pattern recognition. 3- Data comparison. 4- Test against limits & ranges. 5- Correlation of multiple technologies. 6- Statistical process analysis.Proactive Maintenance (root cause maintenance):Proactive Maintenance (root cause maintenance): Improves maintenance through better designinstallation, maintenance activities, work men ship and scheduling.Characteristics of proactive maintenance: 1- Using feedback and communications to ensure that changes in design or procedures are rapidly made available to designers and managers. 2- Employing a life cycle view of maintenance and supporting functions. 3- Ensuring that nothing affecting maintenance and it is occurs in isolation. 4- Employing continuous process of improvement.
  4. 4. Motasem Abushanap 5- Optimizing and tailoring maintenance techniques and technologies to each application. 6- Integrating functions that support maintenance into program planning. 7- Using root cause failure and predictive analysis to maximize maintenance effectiveness. 8- Adopting an ultimate goal of fixing components permanently. 9- Periodic evaluation of technical content and performance intervals of maintenance tasks (PM & PT&I).Essential techniques to extend the component life or reach its designed life: 1- Specifications of new/rebuilt components. 2- Commissioning. 3- Precision rebuild and installation. 4- Failed components analysis. 5- Root cause failure analysis. 6- Reliability engineering. 7- Rebuilt certification/verification. 8- Age Exploration (AE) and the relationship with replacement of obsolete items (ROI). 9- Recurrence control.Applications of maintenance strategies:Strategy ApplicationsReactive 1- Industry. 2- Factories. 3- Everywhere where unplanned failure takes place.Preventive 1- US Navy. 2- Cars and automobile. 3- Lubricated systems. 4- Calibrated systems. 5- Everywhere when failure pattern is known.Predictive 1- US navy. 2- NASA technologies. 3- Electrical Surveys. 4- Mechanical Surveys. 5- HVAC systems. 6- Building Surveys.Proactive 1- Controlling Lubricant fluids. 2- Controlling Hydraulic fluids. 3- Controlling Coolants. 4- Controlling Air. 5- Controlling Fuel. 6- HVAC systems.Reliability Centered Maintenance 1- Aviation Industry. 2- Spacecraft Industry. 3- Nuclear Industry. 4- Department of Defense in US.